This invention relates to an optical pattern projecting apparatus and, more particularly, to an optical pattern projecting apparatus for use in manufacture of an optical disk semiconductor device or a mask such as a photo mask for LSIs.
FIG. 14 illustrates an optical system of a known optical pattern projecting apparatus. In the known optical pattern projecting apparatus, as illustrated in FIG. 14, a laser oscillator 101 such as a KrF excimer laser is disposed therein. On the axis of a laser beam emitted from the laser oscillator 101, a relay lens 102, a beam generator member 103 and a condenser lens 104 are disposed in turn so that each is perpendicular to the axis of the laser beam. As seen from FIG. 14, the relay lens 102 comprises a concave lens 102a and a convex lens 102b disposed under the concave lens 102a.
In the known optical pattern projecting apparatus as described above, the laser beam emitted from the laser oscillator 101 is diverged by the concave lens 102a of the relay lens 102 and converted by the convex lens 102b into a parallel beam along the axis of the laser beam. The laser beam passes through the beam generator member 103 which is disposed under the relay lens 102, and the laser beam is condensed and focused by the condenser lens 104 onto a surface of a Si wafer 105 to project a circuit pattern thereon.
FIG. 15 illustrates an optical system of another known optical pattern projecting apparatus which is useful in projecting a more minute circuit pattern on the wafer 105. A fine circuit pattern is useful in increasing the capacity of the semiconductor device. In FIG. 15, a zonal ringed diaphragm 106 is used in place of the beam generator member 103 illustrated in FIG. 14 for shielding low NA (numerical aperture) components of the parallel light beam, which have comparatively low NAs, and generating a zonal ringed beam for illumination, whereby the resolution becomes comparatively good. The zonal ringed diaphragm 106 comprises an annular diaphragm 107 and a disk-shaped diaphragm 108 having a small outer diameter and concentrically disposed in the ringed diaphragm 107.
In the known optical pattern projecting apparatus as described above, since the low NA components are shielded by the zonal ringed diaphragm 106, the resolution becomes good, but the power of the beam has been undesirably lost.